What ever you decide on---double it. You WILL fill it up in a short time. 24x40 x14 (5/12 pitch) with 3 rollups and insulated on slab was about 12k total. with stood 2 direct hurricanes with cosmetic damage only. Watch your building codes. Erection cost about $2 a square. Easy enough to do yourself though. Mine started as a 4 bay, it's down to 1 1/2 now